153 lines
5.1 KiB
C
153 lines
5.1 KiB
C
/*
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* Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The OpenAirInterface Software Alliance licenses this file to You under
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* the OAI Public License, Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.openairinterface.org/?page_id=698
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*-------------------------------------------------------------------------------
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* For more information about the OpenAirInterface (OAI) Software Alliance:
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* contact@openairinterface.org
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*/
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/*! \file PHY/LTE_TRANSPORT/pcfich.c
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* \brief Top-level routines for generating and decoding the PCFICH/CFI physical/transport channel V8.6 2009-03
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* \author R. Knopp
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* \date 2011
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* \version 0.1
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* \company Eurecom
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* \email: knopp@eurecom.fr
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* \note
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* \warning
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*/
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#include "PHY/impl_defs_top.h"
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#include "PHY/defs_eNB.h"
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#include "PHY/LTE_REFSIG/lte_refsig.h"
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//#define DEBUG_PCFICH
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extern uint8_t pcfich_b[4][32];
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void pcfich_scrambling(LTE_DL_FRAME_PARMS *frame_parms,
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uint8_t subframe,
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uint8_t *b,
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uint8_t *bt)
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{
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uint32_t i;
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uint8_t reset;
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uint32_t x1, x2, s=0;
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reset = 1;
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// x1 is set in lte_gold_generic
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x2 = ((((2*frame_parms->Nid_cell)+1)*(1+subframe))<<9) + frame_parms->Nid_cell; //this is c_init in 36.211 Sec 6.7.1
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for (i=0; i<32; i++) {
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if ((i&0x1f)==0) {
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s = lte_gold_generic(&x1, &x2, reset);
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//printf("lte_gold[%d]=%x\n",i,s);
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reset = 0;
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}
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bt[i] = (b[i]&1) ^ ((s>>(i&0x1f))&1);
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}
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}
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void generate_pcfich(uint8_t num_pdcch_symbols,
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int16_t amp,
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LTE_DL_FRAME_PARMS *frame_parms,
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int32_t **txdataF,
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uint8_t subframe)
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{
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uint8_t pcfich_bt[32],nsymb,pcfich_quad;
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int32_t pcfich_d[2][16];
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uint8_t i;
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uint32_t symbol_offset,m,re_offset,reg_offset;
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int16_t gain_lin_QPSK;
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uint16_t *pcfich_reg = frame_parms->pcfich_reg;
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int nushiftmod3 = frame_parms->nushift%3;
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#ifdef DEBUG_PCFICH
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LOG_D(PHY,"Generating PCFICH in subfrmae %d for %d PDCCH symbols, AMP %d, p %d, Ncp %d\n",
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subframe,num_pdcch_symbols,amp,frame_parms->nb_antenna_ports_eNB,frame_parms->Ncp);
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#endif
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// scrambling
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if ((num_pdcch_symbols>0) && (num_pdcch_symbols<4))
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pcfich_scrambling(frame_parms,subframe,pcfich_b[num_pdcch_symbols-1],pcfich_bt);
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// modulation
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if (frame_parms->nb_antenna_ports_eNB==1)
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gain_lin_QPSK = (int16_t)((amp*ONE_OVER_SQRT2_Q15)>>15);
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else
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gain_lin_QPSK = amp/2;
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if (frame_parms->nb_antenna_ports_eNB==1) { // SISO
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for (i=0; i<16; i++) {
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((int16_t*)(&(pcfich_d[0][i])))[0] = ((pcfich_bt[2*i] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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((int16_t*)(&(pcfich_d[1][i])))[0] = ((pcfich_bt[2*i] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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((int16_t*)(&(pcfich_d[0][i])))[1] = ((pcfich_bt[2*i+1] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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((int16_t*)(&(pcfich_d[1][i])))[1] = ((pcfich_bt[2*i+1] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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}
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} else { // ALAMOUTI
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for (i=0; i<16; i+=2) {
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// first antenna position n -> x0
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((int16_t*)(&(pcfich_d[0][i])))[0] = ((pcfich_bt[2*i] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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((int16_t*)(&(pcfich_d[0][i])))[1] = ((pcfich_bt[2*i+1] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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// second antenna position n -> -x1*
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((int16_t*)(&(pcfich_d[1][i])))[0] = ((pcfich_bt[2*i+2] == 1) ? gain_lin_QPSK : -gain_lin_QPSK);
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((int16_t*)(&(pcfich_d[1][i])))[1] = ((pcfich_bt[2*i+3] == 1) ? -gain_lin_QPSK : gain_lin_QPSK);
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// fill in the rest of the ALAMOUTI precoding
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((int16_t*)&pcfich_d[0][i+1])[0] = -((int16_t*)&pcfich_d[1][i])[0];
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((int16_t*)&pcfich_d[0][i+1])[1] = ((int16_t*)&pcfich_d[1][i])[1];
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((int16_t*)&pcfich_d[1][i+1])[0] = ((int16_t*)&pcfich_d[0][i])[0];
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((int16_t*)&pcfich_d[1][i+1])[1] = -((int16_t*)&pcfich_d[0][i])[1];
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}
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}
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// mapping
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nsymb = (frame_parms->Ncp==0) ? 14:12;
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symbol_offset = (uint32_t)frame_parms->ofdm_symbol_size*(subframe*nsymb);
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re_offset = frame_parms->first_carrier_offset;
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// loop over 4 quadruplets and lookup REGs
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m=0;
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for (pcfich_quad=0; pcfich_quad<4; pcfich_quad++) {
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reg_offset = re_offset+((uint16_t)pcfich_reg[pcfich_quad]*6);
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if (reg_offset>=frame_parms->ofdm_symbol_size)
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reg_offset=1 + reg_offset-frame_parms->ofdm_symbol_size;
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for (i=0; i<6; i++) {
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if ((i!=nushiftmod3)&&(i!=(nushiftmod3+3))) {
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txdataF[0][symbol_offset+reg_offset+i] = pcfich_d[0][m];
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if (frame_parms->nb_antenna_ports_eNB>1)
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txdataF[1][symbol_offset+reg_offset+i] = pcfich_d[1][m];
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m++;
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}
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}
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}
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}
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